Pathology and causes of death in stranded humpback whales (Megaptera novaeangliae) from Brazil

Pathological, morphological, and molecular characterization of the infection by Brachycladium goliath in humpback whale Megaptera novaeangliae

The humpback whale (Megaptera novaeangliae) is a cosmopolitan migratory, seasonal mysticete that frequents the Brazilian coast. Strands of specimens may occur during the migratory stay in the country. In 2021 and 2022, three live humpback whales stranded on the coast of Rio Grande do Sul and Santa Catarina states in southern Brazil. After euthanasia, specimens were necropsied, and organs were thoroughly examined for lesions. Grossly, in all three cases, the liver exhibited multifocal, irregular, firm, white areas on the hepatic capsule, which extended into the parenchyma. On the cut surface, the livers were yellow to pale brown with orangish to greenish areas, the bile ducts were prominent, thickened, and severely dilated, and leaf-shaped flukes were found inside of them. Additionally, one case showed moderate atrophy of the right hepatic lobe. The histological findings included dilation of bile ducts, hyperplasia of the bile duct epithelium, marked inflammatory infiltration of lymphocytes, plasma cells, and eosinophils, and portal fibrosis. The parasite Brachycladium goliath was both morphologically and molecularly identified based on diagnostic key for trematodes and the original description of the species, and the amplification and sequencing of the ITS-2 region, respectively. Even though hepatic injury was not the primary cause of stranding, it may have contributed to the debilitation of the whales. To the authors' knowledge, this is the first study that reports M. novaeangliae as a definitive host of B. goliath and that describes the lesions caused by the parasite in cetaceans.

Mobilization of persistent organic pollutants in humpback whales: Insights from feeding areas in the Antarctic peninsula and Strait of Magellan to migration, breeding, and calving grounds along the Brazilian coast

Southern Hemisphere Megaptera novaeangliae undertake the longest migration, which reflect their exposure to lipophilic contaminants. To assess these changes, persistent organic pollutants were analyzed in blubber samples of humpback whales from three regions: the Antarctic Peninsula (n = 46), the Strait of Magellan, Chile (n = 22), and the Brazilian coast (n = 38). The similarity in PCB and HCB levels between individuals from feeding grounds and breeding grounds suggests contamination during feeding. The whales around the Antarctic Peninsula exhibited a predominance of tetrachlorobiphenyl PCBs. Whales feeding in the Strait of Magellan showed a slight prevalence of 5Cl biphenyls, likely due to their consumption of subantarctic krill species as well as small fishes potentially contaminated by industrial activities in Chile. The dominance of 5-6Cl congeners in whales in Brazil, may be attributed to the extreme physiological changes during fasting when whales utilize blubber reserves and metabolize lighter congeners, or transfer them to their calves.

Evaluating Potential Cetacean Welfare Indicators from Video of Live Stranded Long-Finned Pilot Whales (Globicephala melas edwardii)

Despite the known benefit of considering welfare within wildlife conservation and management, there remains a lack of data to inform such evaluations. To assess animal welfare, relevant information must be captured scientifically and systematically. A key first step is identifying potential indicators of welfare and the practicality of their measurement. We assessed the feasibility of evaluating potential welfare indicators from opportunistically gathered video footage of four stranded odontocete species (n = 53) at 14 stranding events around New Zealand. The first stranded cetacean ethogram was compiled, including 30 different behaviours, 20 of which were observed in all four species. Additionally, thirteen types of human intervention were classified. A subset of 49 live stranded long-finned pilot whales (Globicephala melas edwardii) were assessed to determine indicator prevalence and to quantify behaviours. Four ‘welfare status’ and six ‘welfare alerting’ non-behavioural indicators could be consistently evaluated from the footage. Additionally, two composite behavioural indicators were feasible. Three human intervention types (present, watering, and touching) and five animal behaviours (tail flutter, dorsal fin flutter, head lift, tail lift, and head side-to-side) were prevalent (>40% of individuals). Our study highlights the potential for non-invasive, remote assessments via video footage and represents an initial step towards developing a systematic, holistic welfare assessment framework for stranded cetaceans.

Fundamental Concepts, Knowledge Gaps and Key Concerns Relating to Welfare and Survival of Stranded Cetaceans

Wildlife management can influence animal welfare and survival, although both are often not explicitly integrated into decision making. This study explores fundamental concepts and key concerns relating to the welfare and survival of stranded cetaceans. Using the Delphi method, the opinions of an international, interdisciplinary expert panel were gathered, regarding the characterisation of stranded cetacean welfare and survival likelihood, knowledge gaps and key concerns. Experts suggest that stranded cetacean welfare should be characterised based on interrelated aspects of animals’ biological function, behaviour, and mental state and the impacts of human interventions. The characterisation of survival likelihood should reflect aspects of stranded animals’ biological functioning and behaviour as well as a 6-month post-re-floating survival marker. Post-release monitoring was the major knowledge gap for survival. Welfare knowledge gaps related to diagnosing internal injuries, interpreting behavioural and physiological parameters, and euthanasia decision making. Twelve concerns were highlighted for both welfare and survival likelihood, including difficulty breathing and organ compression, skin damage and physical traumas, separation from conspecifics, and suffering and stress due to stranding and human intervention. These findings indicate inextricable links between perceptions of welfare state and the likely survival of stranded cetaceans and demonstrate a need to integrate welfare science alongside conservation biology to achieve effective, ethical management at strandings.

Microscopic Findings in the Cardiac Muscle of Stranded Extreme Deep-Diving Cuvier's Beaked Whales (Ziphius cavirostris)

Considerable information has been gained over the last few decades on several disease processes afflicting free-ranging cetaceans from a pathologist's point of view. Nonetheless, there is still a dearth of studies on the hearts of these species. For this reason, we aimed to improve our understanding of cardiac histological lesions occurring in free-ranging stranded cetaceans and, more specifically, in deep-diving Cuvier's beaked whales. The primary cardiac lesions that have been described include vascular changes, such as congestion, edema, hemorrhage, leukocytosis, and intravascular coagulation; acute degenerative changes, which consist of contraction band necrosis, wavy fibers, cytoplasmic hypereosinophilia, and perinuclear vacuolization; infiltration of inflammatory cells; and finally, the presence and/or deposition of different substances, such as interstitial myoglobin globules, lipofuscin pigment, polysaccharide complexes, and intra- and/or extravascular gas emboli and vessel dilation. This study advances our current knowledge about the histopathological findings in the cardiac muscle of cetaceans, and more specifically, of Cuvier's beaked whales.

Diseases and parasites

Inuit in Alaska, Canada, and Russia have a long-term tradition in hunting bowhead whales that reaches back several thousands of years. Central to Inuit culture, hunted bowhead whales have undergone rigorous health evaluation by hunters and communities through various iterative processes guided by traditional customary practices. These traditional customary practices are similar to western meat hygiene designed to provide a thorough health assessment of the catch and by default, a public health judgment on food safety. With the establishment of the bowhead whale harvest monitoring program in Utqiaġvik in 1972, led by the North Slope Borough leadership and Alaska Eskimo Whaling Commission (AEWC), collaborative research on the health of bowhead whales between the AEWC, Village Whaling Captains Association, Whaling Captain’s Wives Association, research scientists, and veterinarians have continued to build on the in-depth Inuit knowledge of the bowhead whale. This chapter synthesizes the historic and current knowledge about health and disease conditions of the bowhead whale. The information provided is a coproduction of knowledge reflecting perspectives of Inuit indigenous and local knowledge, veterinary medicine, and biology.

Declining reproductive success in the Gulf of St. Lawrence's humpback whales (Megaptera novaeangliae) reflects ecosystem shifts on their feeding grounds

Climate change has resulted in physical and biological changes in the world's oceans. How the effects of these changes are buffered by top predator populations, and therefore how much plasticity lies at the highest trophic levels, are largely unknown. Here endocrine profiling, longitudinal observations of known individuals over 15 years between 2004 and 2018, and environmental data are combined to examine how the reproductive success of a top marine predator is being affected by ecosystem change. The Gulf of St. Lawrence, Canada, is a major summer feeding ground for humpback whales (Megaptera novaeangliae) in the North Atlantic. Blubber biopsy samples (n = 185) of female humpback whales were used to investigate variation in pregnancy rates through the quantification of progesterone. Annual pregnancy rates showed considerable variability, with no overall change detected over the study. However, a total of 457 photo-identified adult female sightings records with/without calves were collated, and showed that annual calving rates declined significantly. The probability of observing cow-calf pairs was related to favourable environmental conditions in the previous year; measured by herring spawning stock biomass, Calanus spp. abundance, overall copepod abundance and phytoplankton bloom magnitude. Approximately 39% of identified pregnancies were unsuccessful over the 15 years, and the average annual pregnancy rate was higher than the average annual calving rate at ~37% and ~23% respectively. Together, these data suggest that the declines in reproductive success could be, at least in part, the result of females being unable to accumulate the energy reserves necessary to maintain pregnancy and/or meet the energetic demands of lactation in years of poorer prey availability rather than solely an inability to become pregnant. The decline in calving rates over a period of major environmental variability may suggest that this population has limited resilience to such ecosystem change.

Cetacean morbillivirus in Humpback whales' exhaled breath

The humpback whale (HW; Megaptera novaeangliae) population that seasonally resides along the Brazilian coast concentrates in the Abrolhos Bank (Bahia and Espírito Santo states) for breeding during austral winter and spring. Cetacean morbillivirus (CeMV, Paramyxoviridae family) is currently one of the most significant biological threats to cetaceans worldwide with high infection and mortality rates. CeMV is pleiotropic yet it has special tropism for the respiratory, lymphoid and nervous system and is primarily transmitted by the aerogenous route. A new lineage of CeMV, the Guiana dolphin morbillivirus (GDMV), is known to affect cetaceans off Brazil. GDMV was first detected in a Guiana dolphin (Sotalia guianensis) stranded in the Abrolhos Bank region, in 2010. In addition to pathologic examinations on stranded HW, pathogen survey of free-ranging HW may provide valuable insight into the epidemiology of diseases. We hypothesized that HW in the Brazilian breeding ground could be exposed to CeMV. Thus, in the present study, we investigated the presence of CeMV in exhaled breath condensates (EBC) of HW in the Abrolhos Bank. Overall, 73 samples of EBC from 48 groups of HW were collected during the breeding seasons of 2011 (n = 16) and 2012 (n = 57). One sample failed to have the reference gene amplified and was excluded from the study. CeMV was detected by a RT-qPCR method in 2 EBC samples, representing 2 whale groups. Phylogenetic analysis of partial morbillivirus phosphoprotein gene showed 100% homology to GDMV. Our results show that HW in Brazil are infected by CeMV with a relative prevalence of 4.3% (2/47) and demonstrate the suitability of using EBC and RT-qPCR as a non-invasive tool for CeMV survey in free-ranging whales. This pioneer study provides scientific basis for non-invasive CeMV monitoring of HW, suggests HW may play a role in the dynamics of CeMV and raises concern for potential conservation implications for this species.

Skeletal and Cardiac Rhabdomyolysis in a Live-Stranded Neonatal Bryde's Whale With Fetal Distress

The main objective of wildlife forensic investigation is to recognize pathologic changes and cause of death. Even though it may not always be possible to determine the specific illness and/or etiology, the description and subsequent interpretation of the injuries provide an invaluable understanding of pathology in cetacean post-mortem investigations. Although pathological studies have been previously reported in various cetacean species, such descriptions of the infraorder Mysticeti remain rare. A live-stranded neonatal Bryde's whale (Balaenoptera edeni) which subsequently died soon after the stranding, was assessed by physical exam, blood examination, gross necropsy evaluation, histopathology, and immunohistochemistry. It presented with elevated serum levels of creatine kinase, cardiac troponin I, urea, and creatinine. Microscopically, we observed keratin spicules (squamous epithelial cells) and areas of atelectasis in the lungs. Acute degeneration in the myocytes and cardiomyocytes were comparable to the findings previously described in cases of capture myopathy in live-stranded cetaceans. Immunohistochemistry biomarkers such as myoglobin, fibrinogen, and troponin were analyzed. Skeletal and myocardial damage has been documented in several cetacean species. However, this is the first reported case of skeletal and cardiac rhabdomyolysis associated with live-stranding in a newborn Bryde's whale that suffered from fetal distress.

Pathologic findings and causes of death in southern right whales Eubalaena australis, Brazil

Southern right whales Eubalaena australis (SRWs) migrate to southern Brazil for breeding and calving from June through November. Overall, there is scarce knowledge on health status and pathologic conditions in SRWs. We report the pathologic and molecular investigation results of 8 SRWs that were necropsied between 2010 and 2017 within a breeding and calving ground in Santa Catarina state, Brazil. The animals were of various ages (7 newborns/calves, 1 adult) and sex (3 females, 5 males). Five whales stranded dead; 3 stranded alive and died shortly after (n = 2) or were euthanized (n = 1). The causes of stranding and/or death were neonatal respiratory distress syndrome with meconium aspiration (n = 3) with concomitant congenital hepatopathy in one of them; trauma of unknown origin (n = 3), infectious renal and lung disease with presumed sepsis (n = 1), and euthanasia (n = 1). Three animals were PCR-positive for cetacean morbillivirus; one of them also had morbilliviral antigen in kidney via immunohistochemical analysis. These results, integrating novel findings and a published report, contribute to the pathology knowledge of this species.

Omphalitis, urachocystitis and septicemia by Streptococcus dysgalactiae in a southern right whale calf Eubalaena australis, Brazil

Southern right whales Eubalaena australis (SRW) use the southern coast of Brazil as a wintering and calving ground. Other than anthropogenic threats, there is limited knowledge on health and disease aspects for this species. We report the gross and microscopic findings and microbiological identification of streptococcal septicemia in a SRW calf. Main gross findings included fibrinosuppurative omphalitis and urachocystitis, suppurative cystitis, valvular endocarditis and myocarditis, embolic pneumonia, suppurative myositis and osteoarthritis, and lymphadenomegaly. Histological examination confirmed the above inflammatory processes and indicated disseminated Gram-positive coccoid septicemia. PCR analysis, based on the 16S rRNA gene from bacteria isolated on blood agar, identified Streptococcus dysgalactiae. Pathologic and microbiologic analysis indicated that β-hemolytic S. dysgalactiae septicemia, presumably initiated as ascending omphalic infection, was responsible for stranding and death in this individual. These results further confirm pathogenicity of streptococci in cetaceans and add to the limited health and disease related pathology knowledge for this species.

Pathologic findings and causes of death of stranded cetaceans in the Canary Islands (2006-2012)

This study describes the pathologic findings and most probable causes of death (CD) of 224 cetaceans stranded along the coastline of the Canary Islands (Spain) over a 7-year period, 2006-2012. Most probable CD, grouped as pathologic categories (PCs), was identified in 208/224 (92.8%) examined animals. Within natural PCs, those associated with good nutritional status represented 70/208 (33.6%), whereas, those associated with significant loss of nutritional status represented 49/208 (23.5%). Fatal intra- and interspecific traumatic interactions were 37/208 (17.8%). Vessel collisions included 24/208 (11.5%). Neonatal/perinatal pathology involved 13/208 (6.2%). Fatal interaction with fishing activities comprised 10/208 (4.8%). Within anthropogenic PCs, foreign body-associated pathology represented 5/208 (2.4%). A CD could not be determined in 16/208 (7.7%) cases. Natural PCs were dominated by infectious and parasitic disease processes. Herein, our results suggest that between 2006 and 2012, in the Canary Islands, direct human activity appeared responsible for 19% of cetaceans deaths, while natural pathologies accounted for 81%. These results, integrating novel findings and published reports, aid in delineating baseline knowledge on cetacean pathology and may be of value to rehabilitators, caregivers, diagnosticians and future conservation policies.